This application relates to liners for the convergent flaps and seals which are part of a convergent/divergent nozzle for a gas turbine engine, and wherein the liners are formed of two separate plates.
A gas turbine engine typically includes a plurality of sections, which are positioned in series. A fan section moves air downstream towards a compressor section. The compressor section compresses the air and delivers it into a combustion section. In the combustion section, air and fuel are mixed and combusted. Products of combustion pass downstream over turbines, and then outwardly through a nozzle.
It is known in the prior art to vary the cross-sectional area of the nozzle by having flaps that pivot inwardly and outwardly. Typically, a plurality of circumferentially spaced flaps and seals are positioned upstream of a throat, and are called the convergent flaps and seals. Downstream of the throat are divergent flaps and seals. The convergent flaps and seals not only move to define the throat area, but they also provide a block for the products of combustion reaching a housing outboard of the flaps and seals.
In the structure for the convergent flaps and seals, a liner typically faces the products of combustion. The liner is connected by a bracket to the flap or seal.
In the prior art, the liners have been subject to high thermal and external loads. In particular, the liner extends over a portion of the length of the nozzle, and as one moves downstream in the nozzle, the liner is subject to greater heat. This is true for several reasons, one being the fact that cooling air is mixed into the nozzle at a position upstream. This cooling air has lesser and lesser effects as one moves downstream.
The liner is subjected to thermal stresses from this thermal gradient along its length. An aft, or downstream edge, of the liner is hotter than a forward curled edge. Thermal stress from the more aft portion is transferred forward toward the forward edge. On the other hand, external loads such as from structure for moving the liner and the associated seal or flap are largely on the upstream of forward portion. These external loads are transferred back toward the aft portion.
Typically, a backing sheet has been attached to the liner by rivets, which are in tension. It is undesirable to have rivets loaded in tension.
In the prior art, a separate plate has been utilized to provide a flow blocker to maintain a higher pressure forward, or upstream, of the flow blocker, and the lower pressure downstream of the flow blocker. The requirement of this separate flow blocker plate adds additional structure, which is undesirable.